The evolving world of telecommunications is continuously providing various technological advancements for enabling the reliable transmission and reception of data information. As the need for more data increases with the seductive lure of multimedia data services such as video phone capabilities, MP3 downloading, video downloading, and other such content, so does the need for increased communication bandwidth, communication link reliability, and communication link resource management. These established needs especially apply to the area of wireless communications, since within any geographical region supporting wireless communications, finite and limited communication spectrum resources are shared among multiple users.
Wireless communication systems generally use, among other things, data compression, data modulation techniques, protocols, and access technologies for utilizing/sharing transmission bandwidth. There are numerous multiplexing techniques in the field of wireless communications that allow a plurality of user terminals, such as cell phones, TV channels, WiFi devices, BlueTooth devices etc., to share a common transmission resource. Such shared common resources may include, among other things, the transmission bandwidth, or one or more portions of the radio frequency spectrum.
Access technologies provide communication channels to various users by allocating transmission time, transmission frequency, both transmission time and transmission frequency, or by utilizing other techniques such as the application of unique codes (e.g., Pseudo Random Binary Sequences) in an attempt to facilitate the sharing of the wireless communication spectrum among various users. Some examples of existing access technologies are Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), Code Division Multiple Access (CDMA), and Orthogonal Frequency Division Multiplexing (OFDM).
RF channels used by current wireless communication technologies adopting access techniques such as FDMA, TDMA, CDMA, and OFDM are usually pre-designed. Namely, the channels are defined either in frequency, in time, in frequency and in time, or in frequency and codes. In principle, generally, users share a piece of spectrum and release it when communication is completed. For example, GSM accommodates more than 8 simultaneous calls within a 200 kHz channel (8 time slots allocated per 200 KHz), CDMA accommodates around 50 calls per 1.25 MHz (where 64 Walsh codes are allocated) of allocated bandwidth, while 3GPP/UMTS may simultaneously accommodate 128 calls within a 5 MHz spectrum. FIGS. 1A-1E illustrate some of these known access techniques.
FIG. 1A illustrates spectral resource allocation in systems adopting FDMA, where the spectrum is divided into smaller disjoint frequency bands (i.e., b1-b6) each representing a communication channel (i.e., n1-n6). In FDMA, each channel uses the frequency band for the entire time. Systems that may use FDMA are, for example, TV and music broadcasting systems. As shown in FIG. 1B, FDMA systems use guard bands in order to avoid adjacent channel interference. In contrast to FDMA, FIG. 1B also illustrates the allocation of spectrum in OFDM systems. OFDM uses many subcarriers/tones to carry information. Data information associated with each user is encoded onto multiple overlapping subcarriers/tones. Since these subcarriers/tones are orthogonal to each other, no adjacent channel interference is experienced. However, the overlapping subcarriers/tones facilitate an increase in spectrum utilization from a frequency allocation perspective. Systems that use OFDM are, for example, 802.11, 802.16x, WiMAX, 802.20, Wibro (Korea) 3GPP LTE, UMB, DVB-T, and DVB-H. FIG. 1C illustrates spectral resource allocation in systems adopting TDMA, where each channel (i.e., n1-n6) utilized the entire spectrum for a certain amount of time (i.e., t1-t6). FIG. 1D illustrates spectral resource allocation in systems adopting both frequency and time multiplexing, where each channel (e.g., n1) is assigned a certain frequency band (e.g., f1) for a certain amount of time (e.g., t1). The adoption of such a spectrum allocation methodology includes dividing the frequency and time map (or plan) into rectangles. GSM systems are among those that utilize both frequency and time multiplexing such as that illustrated in FIG. 1D. FIG. 1E illustrates spectral resource allocation in systems adopting CDMA, where each channel (i.e., c1-c6) has a unique code. As illustrated, all the channels (e.g., c1-c6) use the entire frequency spectrum (i.e., F), the entire transmission time (i.e., T), and each individual channel is allocated a certain portion of power (i.e., P1-P6).
The data information carrying waveforms (i.e., carrier signals) used by these access technologies are also pre-designed with a view to keeping adjacent channels well separated for avoiding/reducing inter-channel interference. For example, GSM uses a Gaussian like waveform, W-CDMA uses a root raised cosine (RRC), and OFDM uses rectangular pulses. Therefore, providing data information carrying waveforms that permit efficient spectrum utilization while maintaining channel integrity is highly desirable.
According to at least one aspect, a novel system and method for utilizing transmission bandwidth within a communication spectrum is provided.